Introduction1. How to Retrieve Data From a Single Table1.1. The Five Clauses of the SELECT Statement1.2. Column Specifications1.3. LIKE and REGEXP Operators1.4. Arithmetic Operators1.5. Column Aliases1.6. Comparison Operators1.7. IS NULL, BETWEEN, IN Operators1.8. AND, OR, NOT Logical Operators1.9. DISTINCT Clause2. How to Retrieve Data from Multiple Tables2.1. The JOIN Clause2.2. Joining More Than Two Tables2.3. The OUTER JOIN Clause2.4. How to Code a UNION3. Using Functions3.1. Date Functions3.2. Numeric Functions3.3. String Functions4. How to Insert, Update, Delete Data in Tables4.1. The INSERT Clause With a Column List4.2. The INSERT Clause Without a Column List4.4. The UPDATE Clause With a Column List4.4. The DELETE Clause5. Summary Queries and Aggregate Functions5.1. Aggregate Functions5.2. Grouping Data5.3. Simple GROUP BY Query5.4. Improving the GROUP BY Query5.5. Using the HAVING Clause5.5. Using the HAVING and WHERE Clauses Together5.6. COUNT(column_name) and COUNT(*)5.7. Using the DISTINCT Statement6. Working With Subqueries6.1. The Subquery In a SELECT Statement6.2. The Subquery in an UPDATE statement6.3. Create a Duplicate Table From An Existing Table 6.4. The Subquery In a Delete Statement7. SQL Views7.1. SQL View Explained7.2. Benefits of Using Views7.3. Views That Allow UPDATE Statements8. SQL Indexes8.1. SQL Indexes Explained8.2. Clustered vs. Non-clustered Indexes8.3. Create an Index in Workbench Using an ERD8.4. How to Manually Add an Index to an Existing TableGlossaryIndex
3.2

Numeric Functions

ROUND

  • The ROUND function has two parameters. The first is a number, usually a DECIMAL or a FLOAT. The second defines the number of decimals to which the number will be rounded.
  • If no length is provided, the number is rounded to a whole number.

Table 5. ROUND function

Function

Type

Example

Result

ROUND(number[, length])

Number

ROUND(13.37, 1)

13.4

Example:

USE world;
SELECT name, LifeExpectancy, ROUND(LifeExpectancy) 
FROM world.country;

Results:

05_functions.png

FLOOR, CEILING, TRUNCATE

  • FLOOR() will return the next lowest whole number no matter what the decimal point.
  • CEILING() will return the next highest whole number no matter what the decimal point.
  • TRUNCATE() will return the number truncated to the precision specified.

Table 6. FLOOR, CEILING, TRUNCATE functions

Function

Type

Example

Result

FLOOR(number)

number

FLOOR(7.7)

7

CEILING(number)

number

CEILING(6.2)

7

TRUNCATE(NUMBER, length)

number

TRUNCATE(7.9)

7

Example:

USE bike;
SELECT list_price, FLOOR(list_price), CEILING(list_price),
    TRUNCATE(list_price, 0)
FROM product;

Results:

06_functions.png